Residual current devices, which are also referred to as ground fault circuit interrupters (GFCIs), have been in use worldwide for over forty years, and these devices have contributed significantly to the reduction in fatal accidents arising from electric shock. The principle of operation of RCDs will be well known to those versed in the art, but detailed information can be found in the article “Demystifying RCDs”, at www.rcd.ie, which is incorporated herein by reference in its entirety.
RCDs are fitted with a test device, often a manually operable button, to enable the user to verify the correct operation of the device, but if the RCD fails to trip on operation of the test device the user may be tempted to simply disregard this warning sign of failure or may delay unduly in replacing the RCD. Once the RCD has failed for any reason it ceases to provide any protection and should be replaced immediately.
It is an object of the invention to provide an RCD, or other fault detecting device such as an AFD, which incorporates means to remove power from the load in the event of the device failing to trip when operated by the test device. This is sometimes referred to as “end of life” operation or an “end of life” condition.